The presence of hemicellulose impurities such as xylan acetates, and to a lesser degree, glucomannan acetates, in cellulose triacetate (CTA) tends to increase the concentrated solution viscosity of the CTA. This effect in which one CTA exhibits a higher concentrated solution viscosity relative to another CTA of the same intrinsic viscosity (IV) is called the false viscosity effect. Properties such as tensile and tear strength are closely related to molecular weight distribution, which is reflected by IV rather than concentrated solution viscosity.
Cellulose triacetate films are used in various photographic or optical elements because they are tough and have flame retardant properties. Generally, cellulose triacetate film has wide acceptance as a photographic support material. Recently, cellulose triacetate film has been used in the manufacture of liquid crystal displays or LCDs due to the film having an optical isotropy. The cellulose triacetate film is used as a protective film of a polarizing plate or a color filter in the liquid crystal display device.
In the case of LCD devices with higher resolution and brightness, smaller pixel size will be needed. Birefringent particles in the CTA protective film scatter light and interfere with the image clarity. Therefore, there is a need for even lower levels of birefringent particles in the CTA film. A CTA with lower viscosity in film casting solutions can be filtered through smaller openings in the same time as can conventional CTAs. This allows production of higher quality film while minimizing production cost. There is also a need for a cellulose triacetate having sufficiently high strength, low false viscosity, and relatively low peeling resistance for use in optical devices that can be made less expensive relative to a cellulose triacetate made from cotton linters.